I got an interesting info from Hypex about the adapter board they are selling, that I though I would share here as the main ncore thread is now closed for good.

The SMPS600 is often preferred to the SMPS1200 when used with the nc400 as it does provide the necessary Vdr (16V min) to prevent the use of the internal regulator of the nc400n thus saving ~5W of power dissipation.

The SMPS1200A400 only provides 15.6V, which is sadly not enough for the need here (albeit it might work...).

So, going back to the adapter, it appears it does include a diode that raises the effective Vdr by 1V, making it just right for the nc400

A simple SMPS1200 now appears to be a no-brainer solution compared to two SMPS600 when powering a pair of nc400, as it is the same price as a SMPS600, has what appears to be a better heatsink design, and only dissipate 1.5W more watts than a single SMPS600 when idle (9W vs 7.5W), so 6W less than a pair of SMPS600.
Oh, and it does have a clean dual adapter solution to connect the modules, saving the trouble of building a Y cable

Just stumbled across this thread as i have the adapter board in question. I've ordered some parts from Hypex not so long ago and they kindly offered this adapter. Managed to elevate the pater PCB board (above the PSU) by using long plastic spacer on one of the SMPS12400 PSU mounting screws. I really appreciate SMPS1200 heatsink design, as I could apply the thermal paste underneath for better contact with the case, so that heat is transferred to the case itself, acting as one big heatsink (same procedure was put in place for NC400 modules)

Here is the photo of the new set-up.

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My nc400 looks to need a recapping after roughly 4 years, at least some of the SMPS caps appear to be getting weak, it won't always startup on a cold start anymore, sometimes taking an hour to finally power on. (accidentally found this out one day when I left it turned on and left music playing)

That said, this comes back to the 10W of waste heat the amp consumes doing SFA due to the reasonings Hypex have for keeping the SMPS1200 @15.6V vdr in the first place, one would have thought they have a jumper for the DIY nc400 modules in a newer revision SMPS1200 for a 15.6/16V switch, and yes they have revised the PSU at least once or twice.

I have ordered a tiny 15VA 18/18V toroid (after having success using 3 of these really cute things in my dam1021 build), to add the required floating 16-24V (big range) regulated Vdr for the nc400, reducing its effective idle dissipation.

My nc400 looks to need a recapping after roughly 4 years, at least some of the SMPS caps appear to be getting weak, it won't always startup on a cold start anymore, sometimes taking an hour to finally power on.

Wow, this is extremely disturbing!! I’ve had mine for longer than that... better check them out